The quake occurred at around 2:29 p.m. some 9 kilometers north of Pohang and a series of aftershocks followed, the Korea Meteorological Administration said. A quake that struck South Korea last year at magnitude 5.8 in the nearby city of Gyeongju is the only stronger one on record.
The initial quake, the second largest on record in South Korea, was followed by a 4.6-magnitude quake at about 4:49 p.m.
According to the Ministry of Interior and Safety, no fatalities were immediately reported to the authorities. As of 5 p.m., 10 light injuries were reported in Daegu and the North Gyeongsang Province area.